SEISMIC PERFORMANCE EVALUATION AND DAMAGE EVOLUTION ANALYSIS OF SELF-CENTERING BRACED STEEL FRAME

To study the seismic resilience and damage evolution law of braced steel frames before and after the failure of self-centering energy dissipation braces (SCED), a single-span three-storey self-centering braced steel frame (SCBSF) was designed. The refined finite element model was established to investigate the influence of the second stiffness and friction force of braces on macroscopic responses of structures and the damage state of key components, considering the failure of braces. The results indicate that the SCED brace as the first seismic line of SCBSF provides stable energy dissipation and excellent self-centering behavior after activation. Compared with the buckling restrained braced (BRB) frame, the residual interstorey drift ratio of the SCBSF is reduced by 84.9%, significantly reducing the repair costs of structures after earthquakes. When the brace begins to fail after reaching its maximum stroke, the interstorey drift of the frame aggravates, and the plastic energy dissipation ratio of frame beam to column increases by 92.33%; the damage value of the main frame increases by 48.45%; and the seismic performance and resilience level of the structure decrease obviously. The results of parameter analysis show that increasing the stiffness and the friction force of the brace can effectively reduce the structural response. However, when the braced frame with large second stiffness and friction force is still unable to resist strong earthquakes, the number of brace failure may increase, causing structural damage aggravation. Thus, it is necessary to appropriately improve the second stiffness and friction force when designing SCED braces. It is suggested that: the second stiffness should be 7/50-4/25 of the first stiffness; the ratio of friction to pre-pressed force should be 1-1.2. The damage control effect of increasing the second stiffness of the brace is better than that of increasing the friction force. With the increase of ground motion intensity, the influence of friction force and the second stiffness on the seismic performance of braced frames decreases gradually.